1. Technical Field
The present invention relates to an atom cell, a quantum interference device, an atomic oscillator, an electronic apparatus, and a moving object.
2. Related Art
As oscillators having high-accuracy oscillation characteristics on a long-term basis, atomic oscillators that oscillate based on energy transition of atoms of alkali metals including rubidium and cesium are known.
Generally, the operation principle of the atomic oscillators is roughly classified into a system using a double resonance phenomenon by light and microwave and a system using a quantum interference effect (CPT: Coherent Population Trapping) by two kinds of lights having different wavelengths.
In either system of atomic oscillator, typically, an alkali metal is enclosed within a gas cell (atom cell) and the gas cell is heated to a predetermined temperature by a heater so that the alkali metal may be kept in a fixed gas condition.
Or, for example, as disclosed in Patent Document 1 (JP-A-2013-38382), generally, an excessive alkali metal is enclosed in consideration of reduction over time of the alkali metal within the gas cell. The excessive alkali metal is precipitated (condensed) in a part at the lower temperature of the gas cell and exists as a liquid.
However, in related art, the excessive alkali metal attaches to a passage region of excitation light, an amount of excitation light applied to the alkali metal varies and decreases, and thereby, the frequency varies and, as a result, a problem of reduction in frequency stability arises. Particularly, when the atomic cells become smaller with recent requests for downsizing of atomic oscillators etc., the temperature difference between the excitation light passage region and the other regions becomes smaller and the alkali metal attaches to the excitation light passage region more easily, and thereby, the problem becomes significant.